The GrpE protein from E. coli is an essential component of the heat shock protein 70 (Hsp70) molecular chaperone machine which also includes the DnaJ and DnaK proteins. These proteins work together to help facilitate proper protein folding by preventing proteins from going down unwanted pathways such as protein aggregation. They are also involved in the transport of proteins across membranes and the assembly and disassembly of large protein and or protein/DNA complexes. GrpE has some very interesting and unique features concerning its homodimeric structure. There is a long "tail" region at the NH2-terminal end that is composed of two alpha-helices paired together (one from each monomer), and also there is an extended polypeptide from each monomer at the very end that are not paired. The dimer interface includes the "tail" and a four-helix bundle region where each monomer contributes two short ahelices. There is also a beta-sheet domain at the COOH-terminal end that is not involved in the dimer interface. The interaction between GrpE and DnaK takes place between only one of the two monomers in the dimer structure of GrpE and mainly with the beta-sheet domain. The goal of the proposed research is to learn more about the structure of the GrpE protein with emphasis on these unique structural features and interaction with DnaK. Additionally, there are goals that are aimed at investigating mechanisms and rules that govern protein oligomerization and folding. Insight into the mechanisms for the formation of a protein with a four-helix bundle at the dimer interface (GrpE) will help contribute the general knowledge about protein structure and folding. Experimentally, a mutational approach will be taken. Specific sequence deletion mutants of GrpE that contain certain regions of the protein will be created and then tested for functions, such as dimerization, interaction with DnaK. Point mutants will also be created to test the function of salt bridges within the dimer interface. An internal deletion mutant is proposed that will potentially lead to only a monomer of GrpE.